As a device for determining a detailed coordinate position thereof by interpolation of the coordinates of an input position coming in contact with a finger or the like with the output values of sensors of a touch panel, there is “a coordinate input device and a coordinate input system” disclosed in Patent Document 1, for example. This coordinate input device determines a detailed coordinate position on the basis of the magnitudes of electrostatic capacitances produced by the contact finger on the sensors of the touch panel arranged in a strip shape.
FIG. 11 is a diagram (cross-sectional view of a touch panel) for illustrating how to determine a coordinate position by a coordinate input device disclosed in Patent Document 1: Reference numerals 4, 5, 6, 7 and 8 designate sensors, numeral 20 designates a finger, numeral 30 designates an overlay 30 disposed on the sensors, and reference sign L designates each width of the finger 20 and the sensor. In this example, the finger 20 is in contact at a position displaced from the sensor 6 by a distance d toward and over the sensor 7. Here, C1 represents the magnitude of an electrostatic capacitance due to an overlapping portion (L−d) between the finger 20 and sensor 6; C2a represents the magnitude of an electrostatic capacitance due to an overlapping portion (d) between the finger 20 and the sensor 7; C2b represents the magnitude of an electrostatic capacitance produced toward the sensor 7 through the overlay 30 from the portion other than the overlapping portion (d), that is, the portion (L−d); and C3 represents the magnitude of an electrostatic capacitance produced toward the sensor 5 through the overlay 30 from the overlapping portion (L−d) between the finger 20 and sensor 6. Then, it is contemplated that the distance d is determined taking account of the effects of the above capacitances C3 and C2b, and that the detailed coordinate position is determined based on the distance.